The present invention relates to an electronic component (including a semiconductor device and another chip component) having leads for preventing peeling-off of the component due to the warpage of a substrate during wave-soldering, to a manufacturing method thereof, to electronic equipment having such a semiconductor device mounted thereon and to a manufacturing method thereof.
As a method for soldering of a circuit substrate such as an organic substrate of electrical appliances, a reflow soldering process wherein hot-air is blown onto the circuit substrate so that solder paste printed on electrodes is molten to solder a surface mount device (electronic component), and a wave-soldering process wherein molten solder jet is brought into contact with a bottom surface of the substrate to solder to electrodes of a component lying on the bottom surface of the substrate have become the mainstream. Then, today, products requiring for miscellaneous components to be implemented therein by using both of the processes are increased.
However, when a wave-soldering process follows a reflow soldering process, various problems may occur.
One of the problems is that the solder soldered during the reflow process on connection portions of an electronic component may be molten again due to the effect of heat transferred through a substrate during the subsequent wave-soldering process, and connection strength may lower, causing peeling of the electronic component. This problem occurs frequently, particularly when less-toxic Pb-free solder is used. More specifically, when Sn—Ag—Cu alloy solder or Sn—Ag—Cu—Bi alloy solder used for reflow soldering of a low heat-resistance component is used, low-temperature eutectic phase is created owing to segregation of solder constituents, and therefore a connection portion is easily molten again during the subsequent wave-soldering process. For example, in the case of Sn—Ag—Cu—Bi alloy solder used, low-temperature eutectic phase at a melting point of 138° C. is usually created owing to segregation of solder constituents, and very low-temperature eutectic phase at a melting point of 97° C. is created in the connections connected to connection portions of a connected component in which Pb is mixed. Accordingly, re-melting during the wave-soldering can not be avoided.
Further, another problem is substrate warpage caused by heat during wave-soldering, and when a substrate has a curvature due to the warpage, similar to the problem above, peeling of an electronic component may occur. It is generally said that the larger a size of the electronic component becomes, the more this peeling of the electronic component is likely to occur. It is because that the larger the size of the component is, the greater variations of heights of solder connection portions in the vertical direction (the Z-direction) to a surface of the substrate become.
The problem of re-melting and the problem of substrate warpage above occur concurrently, and their combination makes the problem of peeling of a component appear more significantly during a wave-soldering process after a reflow soldering process.
As a countermeasure against the problem of peeling of a component due to re-melting described above, it has been proposed that Sn—Ag—Cu—In alloy solder is used during a reflow process (for example, see JP-A-2005-26393). Sn—Ag—Cu—In alloy solder allows low-temperature soldering to be carried out and it may be used for reflow soldering of a low heat-resistance component, and on the other hand, In among the constituents of the solder and Sn, the main constituent of the solder, may be likely to form solid solution and the formed solid solution maintains similar properties as the main constituent Sn, so that this solder has a feature that low-temperature eutectic phase having a low-temperature melting point may not be likely to be created, and therefore it is effective.
Further, as another countermeasure, it is assumed that if substrate warpage occurs, nonoccurrence of re-melting does not cause peeling of a component, and it has been proposed that nitrogen gas is blown onto connection portions from the upper surface of a substrate during wave-soldering to cool, thereby preventing re-melting of the connection portions (for example, see JP-A-2003-181631).